Many types of machines use machinery components, i.e., interconnected rotating components, to transfer power from, say, an internal combustion engine or an electric drive motor to some sort of "working" device. The proper functioning of such working device is critical to the primary purpose of the machine. As an example, an electric motor may be used to drive the input shaft of a gear transmission. The transmission output shaft may be coupled to a conveyor drive, a winch drum or the like.
Machinery components such as engines, motors and gear transmissions have rotating shafts supported on bearings. Each such component is intended to be coupled to another component and, ideally, components are coupled together so that the shaft axes of rotation are coincident and coextensive. To state it somewhat differently, ideal perfectly-aligned mounting occurs when the shaft axes are horizontally and vertically aligned with one another.
However, because of normal manufacturing tolerances and alignment practices, ideal perfectly-aligned component mounting rarely occurs. In recognition of that fact, manufacturers of such components and of component couplings select the component shaft bearings and configure the couplings to withstand a certain amount of misalignment. And such manufacturers often specify the maximum amount of misalignment that is acceptable and still achieve reasonable bearing and coupling life.
And alignment in a way that provides acceptable bearing and coupling life is not the only problem facing the machine assembler. Two components may have gears that are enmeshed when the machine is assembled. As an example, a gear transmission may have an output pinion gear that meshes with the large ring gear of a winch drum. Gear alignment is important at least to help assure that instead of being "localized," driving force is imposed along the entire width of gear teeth.
When the machine and, particularly, the components are relatively small, component handling and movement for acceptable shaft-to-shaft alignment is relatively easy at least in that such components can be "placed" and the mounting holes drilled with a rather high degree of precision and ease. On the other hand, there are some machines, e.g., a walking dragline, that are so large, they are assembled "on site." (Merely as an example, a large dragline may have a bucket capacity of 80 cubic yards, a weight of 8 million pounds and take upwards of a year to assemble in the field.
In the case of a product such as a large dragline, subassemblies are fabricated and machined at the factory. Until the advent of the invention, several coincident conditions had to occur to obtain shaft alignment of mounted components. The subassemblies, even though often dimensionally large and weighing several tons, had to have mounting surfaces machined with great precision.
And the components to be mounted on such surfaces had to have their mounting "feet" machined with great precision to be coplanar. Mounting holes in such feet (as well as in the subassembly mounting surface) had to be located precisely and the distance between the axis of the rotating shaft with respect to the plane of the mounting feet had to be accurately known. If attainable at all, the necessary all-around precision can be attained only with great difficulty and/or with the expense of further machining on-site. And, of course, the mounting problem becomes even more difficult on machines, the structural mounting surfaces of which have to be welded on-site.
An alternative to precisely-located mounting holes is to use holes substantially larger than required to accommodate the mating bolt or pin. While such oversize holes make alignment easier, the removal of extra metal reduces the fastener supporting bearing area and permits the bolt or pin to more easily "walk" or move slightly in the hole. Therefore, good alignment, even though once attained, can quickly be lost.
Another known approach to component mounting is by welding rather than using bolts or pins. Welding is not without its problems in that heat associated with welding often distorts metal parts--alignment which was satisfactory before welding can easily become unacceptable after welding. And irrespective of the way in which components are mounted, i.e., by bolts, pins or welds, it has been common practice to install welded-on "chock blocks" as a way to help prevent lateral component shifting over time.
An improved apparatus and method which addresses some of the aforementioned disadvantages would be an important advance in the art.